Blower fan

ABSTRACT

In a blower fan according to a preferred embodiment of the present invention, a stationary portion of a motor portion includes a stator, a bearing portion, and a holding portion to which both the stator and the bearing portion are fixed, while a rotating portion includes a central rotating portion, and an annular cup portion fixed to the central rotating portion. The central rotating portion includes a shaft, a bearing opposing portion, and a cylindrical seal portion. The cup portion includes a cylindrical cup inner wall portion fixed to an outer circumferential surface of the cylindrical seal portion, a cup top plate portion, and a cup outer wall portion. A seal portion having a surface of a lubricating oil defined therein is defined in a seal gap between an inner circumferential surface of the cylindrical seal portion and an outer circumferential surface of the bearing portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a blower fan.

2. Description of the Related Art

Small and high-performance electronic devices, such as notebook PCs, produce a large amount of heat at CPUs and the like inside cases thereof. This makes it important to take measures against the heat. One common measure against the heat is to install blower fans inside the cases to discharge the heat. Meanwhile, there has been a demand for a reduction in the thickness of the notebook PCs. Accordingly, there has also been a demand for a reduction in the thickness of the blower fans.

In a fan disclosed in US 2012/0057966, a shaft and a metallic case arranged radially inside a hub are fastened to each other by laser welding. This makes it possible to reduce the axial dimension of an area over which the shaft and the metallic case are fastened to each other, leading to a reduction in the thickness of a motor.

A reduction in the thickness of a blower fan involves a reduction in the axial dimension of each of blades, resulting in a reduction in the volume of an air to be sent out of the blower fan. An attempt to reduce the thickness of the blower fan while maintaining the air volume necessitates an increase in the ratio of the axial dimension of each blade to that of the blower fan. Meanwhile, an increase in this ratio results in narrowing of axial gaps between each blade and a housing. This may lead to a contact between the housing and any blade if the blade sways during rotation of an impeller.

Here, adoption of a dynamic pressure bearing including a radial dynamic pressure bearing and a thrust dynamic pressure bearing as a bearing of the blower fan comes to mind in order to reduce sway of the blades. However, in a slim-type dynamic pressure bearing, a seal portion in which a surface of a lubricating oil is located is arranged radially outward of a dynamic pressure generation portion, resulting in a relatively large outside diameter of the motor. Moreover, in the blower fan as described in US 2012/0057966, it is necessary to space a stator away from the metallic case radially outwardly in order to prevent, for example, an electrical discharge between the metallic case and the stator during a surge test. This necessity leads to an increase in the outside diameter of the motor. An increase in the outside diameter of the motor leads to a reduction in the radial dimension of each blade, resulting in a reduction in the air volume of the blower fan.

SUMMARY OF THE INVENTION

A blower fan according to a preferred embodiment of the present invention includes a plurality of blades arranged in a circumferential direction about a central axis extending in a vertical direction, and a motor portion arranged to rotate the blades about the central axis. The motor portion includes a stationary portion and a rotating portion supported to be rotatable with respect to the stationary portion, and arranged to have the blades fixed thereto. The stationary portion includes a stator, a bearing portion, and an annular holding portion arranged to have the stator fixed to an outer circumferential surface thereof and to have the bearing portion fixed to an inner circumferential surface thereof. The rotating portion includes a central rotating portion supported by the bearing portion, an annular cup portion fixed to the central rotating portion radially outside the central rotating portion, and a rotor magnet fixed to the cup portion, and arranged radially outside the stator. The central rotating portion includes a shaft inserted in the bearing portion, and arranged to rotate about the central axis relative to the bearing portion; a bearing opposing portion arranged to extend radially outward from an upper end of the shaft; and a cylindrical seal portion arranged to extend downward from the bearing opposing portion radially outside the bearing portion. The cup portion includes a cylindrical cup inner wall portion fixed to an outer circumferential surface of the cylindrical seal portion, a cup top plate portion arranged to extend radially outward from an upper end portion of the cup inner wall portion, and a cylindrical cup outer wall portion arranged to extend downward from an outer edge portion of the cup top plate portion. An inner circumferential surface of the cylindrical seal portion and an outer circumferential surface of the bearing portion are arranged to together define a seal gap therebetween, the seal gap including a seal portion having a surface of a lubricating oil defined therein. An inner circumferential surface of the bearing portion and an outer circumferential surface of the shaft are arranged to together define a radial gap therebetween, the radial gap including a radial bearing portion arranged to radially support the shaft. A lower surface of the bearing opposing portion and an upper surface of the bearing portion are arranged to together define a gap therebetween, and the lubricating oil is arranged in this gap. The shaft, the bearing opposing portion, and the cylindrical seal portion are defined by a single continuous electrically conductive member. The cup inner wall portion, the cup top plate portion, and the cup outer wall portion are defined by a single continuous insulating member. The cup inner wall portion and the holding portion are opposed to each other in the vertical direction with an annular horizontal gap intervening therebetween, radially between the cylindrical seal portion and the stator.

The present invention is able to achieve a reduction in the radial dimension of a motor portion.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a blower fan according to a first preferred embodiment of the present invention.

FIG. 2 is a cross-sectional view of a motor portion and its vicinity according to the first preferred embodiment.

FIG. 3 is a cross-sectional view of a sleeve according to the first preferred embodiment.

FIG. 4 is a plan view of the sleeve.

FIG. 5 is a bottom view of the sleeve.

FIG. 6 is a cross-sectional view of a bearing portion and its vicinity according to the first preferred embodiment.

FIG. 7 is a cross-sectional view of a bearing portion of a blower fan according to a second preferred embodiment of the present invention and its vicinity.

FIG. 8 is a cross-sectional view of a bearing portion of a blower fan according to a third preferred embodiment of the present invention and its vicinity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is assumed herein that an upper side and a lower side in an axial direction parallel to a central axis of a blower fan in FIG. 1 are referred to simply as an upper side and a lower side, respectively. Note that a vertical direction assumed herein may not necessarily correspond with a vertical direction of the blower fan when the blower fan is actually installed in a device. It is also assumed herein that a circumferential direction about the central axis is referred to simply by the term “circumferential direction”, “circumferential”, or “circumferentially”, and that radial directions centered on the central axis are referred to simply by the term “radial direction”, “radial”, or “radially”.

First Preferred Embodiment

FIG. 1 is a cross-sectional view of a blower fan 1 according to a first preferred embodiment of the present invention. The blower fan 1 is a centrifugal fan. The blower fan 1 is, for example, installed in a notebook personal computer (hereinafter referred to as a “notebook PC”), and is used to cool devices inside a case of the notebook PC.

The blower fan 1 includes a motor portion 2, a housing 3, and an impeller 5. The impeller 5 is centered on a central axis J1 extending in a vertical direction. The impeller 5 includes a plurality of blades 51. The blades 51 are arranged in a circumferential direction about the central axis J1. The motor portion 2 is arranged to rotate the blades 51 of the impeller 5 about the central axis J1. The housing 3 is arranged to accommodate the motor portion 2 and the impeller 5.

The housing 3 includes an upper plate portion 31, a lower plate portion 32, and a side wall portion 33. The upper plate portion 31 is arranged to cover an upper side of the blades 51. The lower plate portion 32 is arranged to cover a lower side of the blades 51. The motor portion 2 is fixed to the lower plate portion 32. The side wall portion 33 is arranged to cover a lateral side of the blades 51. The upper plate portion 31, the side wall portion 33, and the lower plate portion 32 are arranged to together define an air channel portion 30 arranged to surround the impeller 5.

Each of the upper and lower plate portions 31 and 32 is made of a metal such as an aluminum alloy or stainless steel, and is defined in the shape of a thin plate. The side wall portion 33 is made of an aluminum alloy, and is molded by die casting. Alternatively, the side wall portion 33 may be molded of a resin. A lower end portion of the side wall portion 33 and an edge portion of the lower plate portion 32 are fastened to each other by screws or the like. The upper plate portion 31 is fixed to an upper end portion of the side wall portion 33 by crimping or the like. Each of the upper and lower plate portions 31 and 32 includes an air inlet 34. The air inlets 34 are arranged above and below the impeller 5. The upper plate portion 31, the side wall portion 33, and the lower plate portion 32 are arranged to together define an air outlet on the lateral side of the blades 51. Note that the lower plate portion 32 is a portion of a stationary portion 21, which will be described below.

FIG. 2 is a cross-sectional view of the motor portion 2 and its vicinity. The motor portion 2 is of an outer-rotor type. The motor portion 2 includes the stationary portion 21, which is a stationary assembly, and a rotating portion 22, which is a rotating assembly. Since a bearing mechanism 4, which is a bearing apparatus, is defined by a portion of the stationary portion 21 and a portion of the rotating portion 22 as described below, the motor portion 2 can be considered to include the stationary portion 21, the bearing mechanism 4, and the rotating portion 22 when the bearing mechanism 4 is regarded as a component of the motor portion 2. The rotating portion 22 is supported by the bearing mechanism 4 to be rotatable about the central axis J1 with respect to the stationary portion 21.

The stationary portion 21 includes a stator 210, a bearing portion 23, a bushing 24, and the lower plate portion 32. The bearing portion 23 has a bottom and is substantially cylindrical and centered on the central axis J1. The bearing portion 23 includes a sleeve 231 and a bearing housing 232. The sleeve 231 is substantially cylindrical and centered on the central axis J1. The sleeve 231 is a metallic sintered body. The sleeve 231 is impregnated with a lubricating oil.

The bearing housing 232 has a bottom and is substantially cylindrical and centered on the central axis J1. The bearing housing 232 is arranged to cover an outer circumferential surface and a lower surface of the sleeve 231. The sleeve 231 is fixed to an inner circumferential surface of the bearing housing 232 through an adhesive. The bearing housing 232 is made of a metal. The sleeve 231 may be fixed to the inner circumferential surface of the bearing housing 232 through press fit, for example. Note that both adhesion and press fit may be used to fix the sleeve 231 and the bearing housing 232 to each other. A radially inner portion of the lower surface of the sleeve 231 is spaced away from an inner bottom surface of the bearing housing 232 in the vertical direction. The lower surface of the sleeve 231 and the inner circumferential surface and the inner bottom surface of the bearing housing 232 are arranged to together define a plate accommodating portion 239.

The bushing 24 is a substantially annular member centered on the central axis J1. The bushing 24 is preferably an insulating member. More preferably, the bushing 24 is made of a resin. The bushing 24 includes a bushing body portion 241 and a bushing projecting portion 242. The bushing body portion 241 and the bushing projecting portion 242 are preferably defined integrally with each other. The bushing body portion 241 is substantially cylindrical and centered on the central axis J1. The bushing projecting portion 242 is also substantially cylindrical and centered on the central axis J1. The bushing projecting portion 242 is arranged to have a radial thickness smaller than that of the bushing body portion 241. The bushing projecting portion 242 is arranged to project upward from an outer periphery portion of an upper surface of the bushing body portion 241.

A lower portion of an outer circumferential surface of the bearing housing 232 is fixed to an inner circumferential surface of the bushing body portion 241 through adhesion or press fit. Note that both adhesion and press fit may be used to fix the bearing housing 232 and the bushing 24 to each other. A lower portion of an outer circumferential surface of the bushing 24 is fixed in a hole portion defined in the lower plate portion 32.

The stator 210 is a substantially annular member centered on the central axis J1. The stator 210 is fixed to the outer circumferential surface of the bushing 24. The stator 210 includes a stator core 211 and a plurality of coils 212. The stator core 211 is defined by laminated silicon steel sheets each of which is in the shape of a thin plate. The stator core 211 includes a substantially annular core back 213 and a plurality of teeth 214 arranged to project radially outward from the core back 213. Each of the coils 212 is defined by a conducting wire wound around a separate one of the teeth 214.

The core back 213 is fixed to the bushing 24 through press fit. An inner circumferential surface 213 a of the core back 213 is fixed to both an upper portion of an outer circumferential surface 241 a of the bushing body portion 241 and a lower portion of an outer circumferential surface 242 b of the bushing projecting portion 242. An upper end of the bushing projecting portion 242 is arranged at a level higher than that of an upper end of the core back 213. Note that adhesion or slight press fit may be used to fix the core back 213 and the bushing 24 to each other. Also note that both adhesion and press fit may be used to fix the core back 213 and the bushing 24 to each other.

As described above, the bushing 24 is a holding portion arranged to have the stator 210 fixed to an outer circumferential surface thereof and to have the bearing portion 23 fixed to an inner circumferential surface thereof. In the motor portion 2, both the stator 210 and the bearing portion 23 are indirectly fixed to the lower plate portion 32, which is a base portion, as a result of the bushing 24 being fixed to the lower plate portion 32.

The rotating portion 22 includes a central rotating portion 28, a cup portion 29, a yoke 261, and a rotor magnet 262. The central rotating portion 28 is supported by the bearing portion 23. The cup portion 29 is a member separate from the central rotating portion 28. The cup portion 29 is annular and centered on the central axis J1. The cup portion 29 is fixed to the central rotating portion 28 radially outside the central rotating portion 28.

The central rotating portion 28 includes a shaft 25, a bearing opposing portion 281, and a cylindrical seal portion 282. The shaft 25, the bearing opposing portion 281, and the cylindrical seal portion 282 are defined by a single continuous electrically conductive member. The central rotating portion 28 is preferably defined by subjecting a metal to a cutting process.

The shaft 25 is substantially columnar and centered on the central axis J1. The shaft 25 is inserted in the sleeve 231 of the bearing portion 23. In other words, the sleeve 231 is arranged to surround the shaft 25 from radially outside. The shaft 25 is arranged to rotate about the central axis J1 relative to the bearing portion 23.

A thrust plate 255 is arranged on a lower end portion of the shaft 25. The thrust plate 255 is substantially in the shape of a disk, and is arranged to extend radially outward from the lower end portion of the shaft 25. A substantially columnar plate fixing portion 256 extending upward is arranged on an upper surface of the thrust plate 255. An outer circumferential surface of the plate fixing portion 256 includes a male screw portion. The shaft 25 includes a hole portion 251 arranged to extend upward from a lower end thereof. An inner circumferential surface of the hole portion 251 includes a female screw portion. The thrust plate 255 is fixed to the lower end portion of the shaft 25 as a result of the plate fixing portion 256 being screwed to the hole portion 251.

The thrust plate 255 is accommodated in the aforementioned plate accommodating portion 239. The upper surface of the thrust plate 255 is a substantially annular surface arranged around the shaft 25. The upper surface of the thrust plate 255 is arranged opposite to the lower surface of the sleeve 231, that is, a downward facing surface in the plate accommodating portion 239, in the vertical direction. The thrust plate 255 and the sleeve 231 are arranged to together define a coming-off preventing portion, whereby the shaft 25 is prevented from coming off the bearing portion 23. A lower surface of the thrust plate 255 is arranged opposite to the inner bottom surface of the bearing housing 232 in the vertical direction.

The bearing opposing portion 281 is arranged to extend radially outward from an upper end of the shaft 25. The bearing opposing portion 281 is substantially in the shape of an annular plate and centered on the central axis J1. The bearing opposing portion 281 is arranged above the bearing portion 23 and opposite to the bearing portion 23 in the vertical direction. The cylindrical seal portion 282 is substantially cylindrical, and is arranged to extend downward from the bearing opposing portion 281. The cylindrical seal portion 282 is continuous with an outer periphery portion of the bearing opposing portion 281. The cylindrical seal portion 282 is arranged radially outward of the bearing portion 23 and radially inward of the stator 210. An inner circumferential surface of the cylindrical seal portion 282 is arranged radially opposite an upper portion of an outer circumferential surface of the bearing portion 23. A seal gap 47 is defined between the inner circumferential surface of the cylindrical seal portion 282 and the outer circumferential surface of the bearing housing 232. A seal portion 47 a, which has a surface of the lubricating oil defined therein, is defined in the seal gap 47.

The cup portion 29 includes a cup inner wall portion 291, a cup top plate portion 292, and a cup outer wall portion 293. The cup inner wall portion 291, the cup top plate portion 292, and the cup outer wall portion 293 are defined by a single continuous insulating member. The cup portion 29 is preferably made of a resin.

The cup inner wall portion 291 is substantially cylindrical and centered on the central axis J1. The cup top plate portion 292 is arranged to extend radially outward from an upper end portion of the cup inner wall portion 291. The cup top plate portion 292 is substantially in the shape of a disk and centered on the central axis J1. The cup outer wall portion 293 is arranged to extend downward from an outer edge portion of the cup top plate portion 292. The cup outer wall portion 293 is substantially cylindrical and centered on the central axis J1.

An outer circumferential surface 291 c of the cup inner wall portion 291 includes an inclined surface which is angled radially outward with increasing height. Preferably, the entire outer circumferential surface 291 c of the cup inner wall portion 291 is defined by an inclined surface which is angled radially outward with increasing height. In other words, the outside diameter of the cup inner wall portion 291 is arranged to gradually increase with decreasing distance from the cup top plate portion 292. The inside diameter of the cup inner wall portion 291 is arranged to be substantially uniform. Therefore, the radial thickness of the cup inner wall portion 291 is arranged to gradually increase with decreasing distance from the cup top plate portion 292.

An inner circumferential surface 291 a of the cup inner wall portion 291 is fixed to an outer circumferential surface 282 a of the cylindrical seal portion 282. The cup portion 29 and the central rotating portion 28 are fixed to each other by an insert molding process. The outer circumferential surface 282 a of the cylindrical seal portion 282 includes an annular recessed portion 282 b arranged to be recessed radially inward. The inner circumferential surface 291 a of the cup inner wall portion 291 includes an annular raised portion 291 b arranged to project radially inward. The raised portion 291 b is arranged in a substantial middle of the inner circumferential surface 291 a of the cup inner wall portion 291 in the vertical direction. The raised portion 291 b is fitted to the recessed portion 282 b.

The shape of each of the raised portion 291 b and the recessed portion 282 b may be modified in various manners. For example, the raised portion 291 b may be replaced with a plurality of projections arranged in the circumferential direction, and the recessed portion 282 b may be replaced with a plurality of recesses to which the projections are fitted. Alternatively, the inner circumferential surface 291 a of the cup inner wall portion 291 may be arranged to include a recessed portion(s), with the outer circumferential surface 282 a of the cylindrical seal portion 282 including a raised portion(s) arranged to be fitted to the recessed portion(s). Alternatively, both the outer circumferential surface 282 a of the cylindrical seal portion 282 and the inner circumferential surface 291 a of the cup inner wall portion 291 may be arranged to include knurled structures, which are defined by projections and recesses fitted to one another.

A lower end of the cylindrical seal portion 282 is arranged at a level lower than that of a lower end of the cup inner wall portion 291. The outer circumferential surface 282 a of the cylindrical seal portion 282 includes a substantially cylindrical surface centered on the central axis J1 below the recessed portion 282 b. A lower end portion of the cylindrical seal portion 282 is arranged opposite to the upper surface of the bushing body portion 241 in the vertical direction. The outer circumferential surface 282 a of the cylindrical seal portion 282 is arranged radially opposite an inner circumferential surface 242 a of the bushing projecting portion 242 below the lower end of the cup inner wall portion 291. The bushing projecting portion 242 is a radially opposing portion arranged radially opposite the cylindrical seal portion 282.

An upper end surface of the bushing projecting portion 242 and a lower end surface of the cup inner wall portion 291 are arranged opposite to each other in the vertical direction. Both the bushing projecting portion 242 and the cup inner wall portion 291 are arranged radially between the cylindrical seal portion 282 and the stator 210. An annular minute horizontal gap 491 extending radially is defined between the upper end surface of the bushing projecting portion 242 and the lower end surface of the cup inner wall portion 291. In other words, the bushing projecting portion 242 and the cup inner wall portion 291 are arranged opposite to each other in the vertical direction with the horizontal gap 491 intervening therebetween. The vertical dimension of the horizontal gap 491 is preferably arranged in the range of about 0.1 mm to about 0.5 mm.

An annular minute vertical gap 492 extending in the vertical direction is defined between the inner circumferential surface 242 a of the bushing projecting portion 242 and the outer circumferential surface 282 a of the cylindrical seal portion 282. The vertical gap 492 is continuous with an inner circumferential portion of the horizontal gap 491, and is arranged to extend downward from the horizontal gap 491. An annular minute intermediate gap is defined between the lower end portion of the cylindrical seal portion 282 and the upper surface of the bushing body portion 241. The intermediate gap is continuous with both a lower end portion of the vertical gap 492 and a lower end portion of the seal gap 47. In other words, the intermediate gap is arranged to loin the lower end portion of the vertical gap 492 and the lower end portion of the seal gap 47 to each other.

The yoke 261 is substantially cylindrical and centered on the central axis J1. The yoke 261 is fixed to an inner circumferential surface of the cup outer wall portion 293. The rotor magnet 262 is substantially cylindrical and centered on the central axis J1, and is fixed to an inner circumferential surface of the yoke 261. In other words, the rotor magnet 262 is indirectly fixed to the inner circumferential surface of the cup outer wall portion 293 through the yoke 261. The rotor magnet 262 is arranged radially outside the stator 210.

Referring to FIG. 1, the blades 51 are directly fixed to an outer circumferential surface of the cup outer wall portion 293. Note that the blades 51 may be indirectly fixed to the outer circumferential surface of the cup outer wall portion 293 through another member such as a blade support portion.

FIG. 3 is a cross-sectional view of the sleeve 231. An upper portion and a lower portion of an inner circumferential surface 231 b of the sleeve 231 include a first radial dynamic pressure groove array 271 and a second radial dynamic pressure groove array 272, respectively, each of which is made up of a plurality of grooves arranged in a herringbone pattern. FIG. 4 is a plan view of the sleeve 231. An upper surface 231 a of the sleeve 231 includes a first thrust dynamic pressure groove array 273 made up of a plurality of grooves arranged in a spiral pattern. FIG. 5 is a bottom view of the sleeve 231. A lower surface 231 c of the sleeve 231 includes a second thrust dynamic pressure groove array 274 arranged in a spiral pattern.

Note that each of the first and second radial dynamic pressure groove arrays 271 and 272 may be defined in an outer circumferential surface of the shaft 25. Also note that the first thrust dynamic pressure groove array 273 may be defined in a region of a lower surface of the bearing opposing portion 281 which is opposed to the upper surface 231 a of the sleeve 231. Also note that the second thrust dynamic pressure groove array 274 may be defined in the upper surface of the thrust plate 255. Also note that the first thrust dynamic pressure groove array 273 may be made up of a collection of grooves arranged in a herringbone pattern. Also note that the second thrust dynamic pressure groove array 274 may also be made up of a collection of grooves arranged in a herringbone pattern.

FIG. 6 is a cross-sectional view of the bearing portion 23 and its vicinity. A lower gap 42 is defined between the thrust plate 255 and the bearing housing 232. Specifically, the lower gap 42 is defined between the inner bottom surface of the bearing housing 232 and the lower surface of the thrust plate 255 and between a side surface of the thrust plate 255 and an inner circumferential surface of a bottom portion of the bearing housing 232. The lubricating oil is arranged in the lower gap 42. A second thrust gap 43 is defined between the lower surface 231 c of the sleeve 231 and an upper surface 255 a of the thrust plate 255. The lubricating oil is arranged in the second thrust gap 43. The second thrust gap 43 is arranged to define a second thrust dynamic pressure bearing portion 43 a arranged to generate a fluid dynamic pressure in the lubricating oil. The lower gap 42 is continuous with an outer circumferential portion of the second thrust gap 43.

A radial gap 41 is defined between an outer circumferential surface 25 a of the shaft 25 and the inner circumferential surface 231 b of the sleeve 231 of the bearing portion 23. A lower end portion of the radial gap 41 is continuous with an inner circumferential portion of the second thrust gap 43. The radial gap 41 includes a first radial gap 411 and a second radial gap 412 arranged below the first radial gap 411.

The first radial gap 411 is defined between the outer circumferential surface 25 a of the shaft 25 and a portion of the inner circumferential surface 231 b of the sleeve 231 in which the first radial dynamic pressure groove array 271 illustrated in FIG. 3 is defined. Meanwhile, the second radial gap 412 is defined between the outer circumferential surface 25 a of the shaft 25 and a portion of the inner circumferential surface 231 b of the sleeve 231 in which the second radial dynamic pressure groove array 272 illustrated in FIG. 3 is defined. The lubricating oil is arranged in the radial gap 41. Therefore, the lubricating oil is arranged in both of the first and second radial gaps 411 and 412. The first and second radial gaps 411 and 412 are arranged to together define a radial dynamic pressure bearing portion 41 a arranged to generate a fluid dynamic pressure in the lubricating oil. The shaft 25 is radially supported by the radial dynamic pressure bearing portion 41 a.

A first thrust gap 44 is defined between an upper surface of the bearing portion 23 and a lower surface 281 a of the bearing opposing portion 281. The first thrust gap 44 is arranged to extend radially outward from an upper end portion of the radial gap 41. The lubricating oil is arranged in the first thrust gap 44. A first thrust dynamic pressure bearing portion 44 a arranged to generate a fluid dynamic pressure in lubricating oil is defined in a region of the first thrust gap 44 in which the first thrust dynamic pressure groove array 273 illustrated in FIG. 4 is defined. That is, a gap defined between the upper surface 231 a of the sleeve 231 and the lower surface 281 a of the bearing opposing portion 281 is arranged to define the first thrust dynamic pressure bearing portion 44 a arranged to generate the fluid dynamic pressure in the lubricating oil.

The bearing opposing portion 281 is axially supported by both the first and second thrust dynamic pressure bearing portions 44 a and 43 a. Provision of the first and second thrust dynamic pressure bearing portions 44 a and 43 a contributes to reducing a variation in vertical play of the shaft 25. The first and second thrust dynamic pressure bearing portions 44 a and 43 a are arranged to be in communication with each other through a circulation groove extending in the vertical direction. The aforementioned seal gap 47 is arranged to extend downward from an outer circumferential portion of the first thrust gap 44.

In the motor portion 2, the seal gap 47, the first thrust gap 44, the radial gap 41, the second thrust gap 43, and the lower gap 42 are arranged to together define a single continuous bladder structure, and the lubricating oil is arranged continuously in this bladder structure. Within the bladder structure, the surface of the lubricating oil is defined only in the seal gap 47, which is located between the inner circumferential surface of the cylindrical seal portion 282 and the outer circumferential surface of the bearing portion 23. The bladder structure contributes to easily preventing a leakage of the lubricating oil.

The bearing mechanism 4 of the motor portion 2 includes the bearing portion 23, the shaft 25, the bearing opposing portion 281, the cylindrical seal portion 282, and the aforementioned lubricating oil. In the bearing mechanism 4, the shaft 25, the bearing opposing portion 281, and the cylindrical seal portion 282 are arranged to rotate about the central axis J1 with respect to the bearing portion 23 through the lubricating oil.

In the motor portion 2 illustrated in FIG. 1, a current is supplied to the stator 210 to produce a torque centered on the central axis J1 between the rotor magnet 262 and the stator 210. This causes the blades 51 of the impeller 5 to rotate about the central axis J1 together with the rotating portion 22. Rotation of the impeller 5 caused by the motor portion 2 causes an air to be drawn into the housing 3 through the air inlets 34 and sent out through the air outlet.

As described above, the shaft 25, the bearing opposing portion 281, and the cylindrical seal portion 282 are defined by a single continuous electrically conductive member. The cup inner wall portion 291, the cup top plate portion 292, and the cup outer wall portion 293 are defined by a single continuous insulating member. The cup inner wall portion 291 is fixed to the outer circumferential surface of the cylindrical seal portion 282. The cup inner wall portion 291 and the bushing 24 are opposed to each other in the vertical direction with the annular horizontal gap 491 intervening therebetween, radially between the cylindrical seal portion 282 and the stator 210.

Accordingly, in the blower fan 1, an improvement in electrical insulation between the central rotating portion 28 and the coils 212 of the stator 210 is achieved. This makes it possible to arrange the central rotating portion 28 and the stator 210 in proximity to each other, making it possible to arrange the stator 210 closer to the central axis J1. This leads to a reduction in the radial dimension of the motor portion 2, leading in turn to an increase in the radial dimension of each of the blades 51. This makes it possible to reduce the vertical dimension of each of the blades 51 to achieve a reduction in the thickness of the blower fan 1 while preventing or reducing a reduction in the air volume.

Moreover, in the blower fan 1, the bushing 24 is also defined by an insulating member. An improvement in insulation between the central rotating portion 28 and the coils 212 of the stator 210 is achieved by each of the bushing 24 and the cup inner wall portion 291. This makes it possible to arrange the stator 210 still closer to the central axis J1. This makes it possible to further reduce the thickness of the blower fan 1 while preventing or reducing the reduction in the air volume.

Regarding the blower fan 1, in the case where the central rotating portion 28 is defined by subjecting the metal to the cutting process, precision with which the central rotating portion 28 is shaped is improved. This enables each of the radial dynamic pressure bearing portion 41 a, the first thrust dynamic pressure bearing portion 44 a, the second thrust dynamic pressure bearing portion 43 a, and the seal gap 47 to be defined with high precision. In the case where the cup portion 29 is made of the resin, a reduction in the weight of the rotating portion 22 is achieved. As a result, a reduction in the power consumption of the blower fan 1 is achieved.

The outer circumferential surface 291 c of the cup inner wall portion 291 includes the inclined surface which is angled radially outward with increasing height. The strength of the cup inner wall portion 291 is thereby increased because the radial thickness of the cup inner wall portion 291 gradually increases with decreasing distance from the cup top plate portion 292. As a result, an increase in strength with which the cup portion 29 and the central rotating portion 28 are fastened to each other is achieved. In the case where the entire outer circumferential surface 291 c of the cup inner wall portion 291 is defined by the inclined surface which is angled radially outward with increasing height, an additional increase in the strength with which the cup portion 29 and the central rotating portion 28 are fastened to each other is achieved.

In the blower fan 1, the outer circumferential surface 282 a of the cylindrical seal portion 282 includes the recessed portion(s) or the raised portion(s), while the inner circumferential surface 291 a of the cup inner wall portion 291 includes the raised portion(s) or the recessed portion(s) to be fitted to the recessed portion(s) or the raised portion(s) of the outer circumferential surface 282 a of the cylindrical seal portion 282. This leads to an additional increase in the strength with which the cup portion 29 and the central rotating portion 28 are fastened to each other.

As described above, the bushing 24 includes the bushing projecting portion 242, the horizontal gap 491 is defined between the bushing projecting portion 242 and the cup inner wall portion 291, and the vertical gap 492 continuous with the horizontal gap 491 is defined between the inner circumferential surface 242 a of the bushing projecting portion 242 and the outer circumferential surface 282 a of the cylindrical seal portion 282. The horizontal gap 491 and the vertical gap 492 are arranged to together define a labyrinth structure radially outside the seal gap 47. This contributes to preventing an air including a lubricating oil evaporated from the seal gap 47 from traveling out of the bearing mechanism 4. In other words, this contributes to reducing evaporation of the lubricating oil out of the bearing mechanism 4.

The outer circumferential surface 242 b of the bushing projecting portion 242 is arranged to be in contact with the inner circumferential surface 213 a of the core back 213, and the upper end of the bushing projecting portion 242 is arranged at a level higher than that of the upper end of the core back 213. This leads to an increased area of contact between the inner circumferential surface 213 a of the core back 213 and the outer circumferential surface of the bushing 24. This in turn leads to an increase in strength with which the core back 213 and the bushing 24 are fastened to each other. Moreover, an increase in the vertical dimension of the aforementioned labyrinth structure is achieved by the upper end of the bushing projecting portion 242 being arranged at a level higher than that of the upper end of the core back 213.

As described above, the bearing portion 23 includes the sleeve 231 and the bearing housing 232. Accordingly, an improvement in flexibility in choosing a material of an inner circumferential bearing portion which constitutes an inner circumferential portion of the bearing portion 23 is achieved. Moreover, in the case where the sleeve 231 is defined by a sintered body, an increase in the amount of the lubricating oil held in the bearing portion 23 is easily achieved.

Second Preferred Embodiment

FIG. 7 is a cross-sectional view of a bearing portion 23 of a blower fan 1 a according to a second preferred embodiment of the present invention and its vicinity. A central rotating portion 28 of the blower fan 1 a includes a cylindrical seal portion 282 e having a different shape from that of the cylindrical seal portion 282 of the central rotating portion 28 of the blower fan 1 illustrated in FIG. 6. The blower fan 1 a is otherwise similar in structure to the blower fan 1. Accordingly, like members or portions are designated by like reference numerals.

As in the blower fan 1, a cup portion 29 and the central rotating portion 28 are fixed to each other by an insert molding process. An outer circumferential surface 282 a of the cylindrical seal portion 282 e is fixed to an inner circumferential surface 291 a of a cup inner wall portion 291. The outer circumferential surface 282 a of the cylindrical seal portion 282 e includes an annular recessed portion 282 b arranged to be recessed radially inward. The inner circumferential surface 291 a of the cup inner wall portion 291 includes a raised portion 291 b arranged to be fitted to the recessed portion 282 b.

The cup inner wall portion 291 and a bushing 24 are opposed to each other in the vertical direction with an annular horizontal gap 491 intervening therebetween, radially between the cylindrical seal portion 282 e and a stator 210. In the blower fan 1 a, as well as in the blower fan 1, an improvement in electrical insulation between the central rotating portion 28 and coils 212 of the stator 210 is achieved. This leads to a reduction in the radial dimension of a motor portion 2, leading in turn to an increase in the radial dimension of each of blades 51 (see FIG. 1). This makes it possible to reduce the vertical dimension of each of the blades 51 to achieve a reduction in the thickness of the blower fan 1 a while preventing or reducing a reduction in air volume.

A lower end of the cylindrical seal portion 282 e is arranged at a level lower than that of a lower end of the cup inner wall portion 291. The outer circumferential surface 282 a of the cylindrical seal portion 282 e includes an inclined surface which is angled radially inward with decreasing height below the recessed portion 282 b. Accordingly, a portion of the outer circumferential surface 282 a of the cylindrical seal portion 282 e between the lower end of the cup inner wall portion 291 and the lower end of the cylindrical seal portion 282 e is an inclined surface which is angled radially inward with decreasing height. This contributes to preventing the outer circumferential surface 282 a of the cylindrical seal portion 282 e from rubbing against a mold when the cup portion 29 and the central rotating portion 28 are fixed to each other by the insert molding process. This contributes to eliminating or reducing the likelihood that a burr will occur at a lower end portion of the cup inner wall portion 291.

The outer circumferential surface 282 a of the cylindrical seal portion 282 e may, for example, include a substantially cylindrical portion centered on a central axis J1 between the recessed portion 282 b and the lower end of the cup inner wall portion 291. Even in this case, if the portion of the outer circumferential surface 282 a of the cylindrical seal portion 282 e between the lower end of the cup inner wall portion 291 and the lower end of the cylindrical seal portion 282 e is the inclined surface which is angled radially inward with decreasing height, the likelihood that a burr will occur at the lower end portion of the cup inner wall portion 291 is eliminated or reduced as in the above-described case.

Third Preferred Embodiment

FIG. 8 is a cross-sectional view of a bearing portion 23 of a blower fan 1 b according to a third preferred embodiment of the present invention and its vicinity. The blower fan 1 b includes a central rotating portion 28 a having a different shape from that of the central rotating portion 28 of the blower fan 1 illustrated in FIG. 6. The blower fan 1 b is otherwise similar in structure to the blower fan 1. Accordingly, like members or portions are designated by like reference numerals.

The central rotating portion 28 a includes a shaft 25, a bearing opposing portion 281, and a cylindrical seal portion 282. A thrust plate 255 is arranged on a lower end portion of the shaft 25. The thrust plate 255 is substantially in the shape of a disk, and is arranged to extend radially outward from the lower end portion of the shaft 25. A substantially columnar plate fixing portion 256 a extending upward is arranged on an upper surface of the thrust plate 255. The shaft 25 includes a through hole 252 arranged to extend in the vertical direction. The plate fixing portion 256 a is press fitted into the through hole 252 from below, whereby the thrust plate 255 is fixed to the lower end portion of the shaft 25. An outer circumferential surface of the plate fixing portion 256 a may be fixed to an inner circumferential surface of the through hole 252 through an adhesive. Both adhesion and press fit may be used to fix the plate fixing portion 256 a and the shaft 25 to each other. The central rotating portion 28 a may, for example, be defined by a press molding process or the like.

Each of an outer circumferential surface 282 a of the cylindrical seal portion 282 and an inner circumferential surface 291 a of a cup inner wall portion 291 is a smooth, substantially cylindrical surface. The outer circumferential surface 282 a of the cylindrical seal portion 282 and the inner circumferential surface 291 a of the cup inner wall portion 291 include no recessed portion(s) or raised portion(s) arranged to be fitted to each other. The central rotating portion 28 a is press fitted radially inside the cup inner wall portion 291, whereby the outer circumferential surface 282 a of the cylindrical seal portion 282 is fixed to the inner circumferential surface 291 a of the cup inner wall portion 291. The outer circumferential surface 282 a of the cylindrical seal portion 282 may be fixed to the inner circumferential surface 291 a of the cup inner wall portion 291 through an adhesive. Both adhesion and press fit may be used to fix the central rotating portion 28 a and a cup portion 29 to each other.

In the blower fan 1 b, as well as in the blower fan 1, the cup inner wall portion 291 and a bushing 24 are opposed to each other in the vertical direction with an annular horizontal gap 491 intervening therebetween, radially between the cylindrical seal portion 282 and a stator 210. As a result, an improvement in electrical insulation between the central rotating portion 28 a and coils 212 of the stator 210 is achieved. This leads to a reduction in the radial dimension of a motor portion 2, leading in turn to an increase in the radial dimension of each of blades 51 (see FIG. 1). This makes it possible to reduce the vertical dimension of each of the blades 51 to achieve a reduction in the thickness of the blower fan 1 b while preventing or reducing a reduction in air volume.

Note that each of the blower fans 1, 1 a, and 1 b may be modified in a variety of manners.

The first thrust dynamic pressure groove array 273 may be defined in the upper surface of the bearing housing 232 or a region of the lower surface of the bearing opposing portion 281 which is opposed to the upper surface of the bearing housing 232. In other words, it is enough that the first thrust dynamic pressure groove array 273 should be defined in at least one of the upper surface of the bearing portion 23 and the lower surface 281 a of the bearing opposing portion 281. As a result, the first thrust dynamic pressure bearing portion 44 a is defined in the first thrust gap 44 defined between the upper surface of the bearing portion 23 and the lower surface 281 a of the bearing opposing portion 281. Note that the first thrust dynamic pressure bearing portion 44 a may not necessarily be defined in the gap 44 between the lower surface 281 a of the bearing opposing portion 281 and the upper surface of the bearing portion 23 as long as the lubricating oil is arranged in the gap 44.

Also note that the bearing housing 232 may not necessarily be defined by a single member. For example, the bearing housing having the bottom and being substantially cylindrical may be made up of a substantially cylindrical “housing cylindrical portion” centered on the central axis J1 and a substantially disk-shaped cap fixed to a lower end portion of the housing cylindrical portion. In this case, the housing cylindrical portion is arranged to cover the outer circumferential surface of the sleeve 231, while the cap is arranged to cover the lower surface of the sleeve 231. Also note that the bearing portion 23 may not necessarily be made up of the bearing housing 232 and the sleeve 231 inserted therein, but may be defined by a single member.

Also note that the lower end of the cylindrical seal portion 282 may not necessarily be arranged at a level lower than that of the lower end of the cup inner wall portion 291, but may be arranged, for example, at substantially the same vertical position as that of the lower end of the cup inner wall portion 291. In this case, the upper surface of the bushing body portion 241 may be arranged opposite to both a lower surface of the cylindrical seal portion 282 and the lower end surface of the cup inner wall portion 291 in the vertical direction without the bushing 24 including the bushing projecting portion 242. This results in the horizontal gap 491 being continuous with the lower end portion of the seal gap 47 without the vertical gap 492 being defined between the seal gap 47 and the horizontal gap 491.

Also note that the bushing 24 may be defined by an electrically conductive member made of a metal or the like, for example.

Also note that, in each of the blower fans 1, 1 a, and 1 b, the air inlet 34 may be defined in only one of the upper and lower plate portions 31 and 32. In other words, regarding each of the blower fans 1, 1 a, and 1 b, it is enough that the upper plate portion 31 or the lower plate portion 32 should include the air inlet 34.

Note that features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises.

Blower fans according to preferred embodiments of the present invention are usable to cool devices inside cases of notebook PCs and desktop PCs, to cool other devices, to supply an air to a variety of objects, and so on. Moreover, blower fans according to preferred embodiments of the present invention are also usable for other purposes. 

What is claimed is:
 1. A blower fan comprising: a plurality of blades arranged in a circumferential direction about a central axis extending in a vertical direction; and a motor portion arranged to rotate the blades about the central axis; wherein the motor portion includes: a stationary portion; and a rotating portion supported to be rotatable with respect to the stationary portion, and arranged to have the blades fixed thereto; the stationary portion includes: a stator; a bearing portion; and an annular holding portion arranged to have the stator fixed to an outer circumferential surface thereof and to have the bearing portion fixed to an inner circumferential surface thereof; the rotating portion includes: a central rotating portion supported by the bearing portion; an annular cup portion fixed to the central rotating portion radially outside the central rotating portion; and a rotor magnet fixed to the cup portion, and arranged radially outside the stator; the central rotating portion includes: a shaft inserted in the bearing portion, and arranged to rotate about the central axis relative to the bearing portion; a bearing opposing portion arranged to extend radially outward from an upper end of the shaft; and a cylindrical seal portion arranged to extend downward from the bearing opposing portion radially outside the bearing portion; the cup portion includes: a cylindrical cup inner wall portion fixed to an outer circumferential surface of the cylindrical seal portion; a cup top plate portion arranged to extend radially outward from an upper end portion of the cup inner wall portion; and a cylindrical cup outer wall portion arranged to extend downward from an outer edge portion of the cup top plate portion; an inner circumferential surface of the cylindrical seal portion and an outer circumferential surface of the bearing portion are arranged to together define a seal gap therebetween, the seal gap including a seal portion having a surface of a lubricating oil defined therein; an inner circumferential surface of the bearing portion and an outer circumferential surface of the shaft are arranged to together define a radial gap therebetween, the radial gap including a radial bearing portion arranged to radially support the shaft; a lower surface of the bearing opposing portion and an upper surface of the bearing portion are arranged to together define a gap therebetween, and the lubricating oil is arranged in this gap; the shaft, the bearing opposing portion, and the cylindrical seal portion are defined by a single continuous electrically conductive member; the cup inner wall portion, the cup top plate portion, and the cup outer wall portion are defined single continuous insulating member; and the cup inner wall portion and the holding portion are opposed to each other in the vertical direction with an annular horizontal gap intervening therebetween, radially between the cylindrical seal portion and the stator.
 2. The blower fan according to claim 1, further comprising a thrust dynamic pressure bearing portion arranged to axially support the bearing opposing portion, and defined in the gap defined between the lower surface of the bearing opposing portion and the upper surface of the bearing portion.
 3. The blower fan according to claim 1, wherein the holding portion is defined by an insulating member.
 4. The blower fan according to claim 1, wherein an outer circumferential surface of the cup inner wall portion includes an inclined surface which is angled radially outward with increasing height.
 5. The blower fan according to claim 2, wherein an outer circumferential surface of the cup inner wall portion includes an inclined surface which is angled radially outward with increasing height.
 6. The blower fan according to claim 1, wherein a lower end of the cylindrical seal portion is arranged at a level lower than that of a lower end of the cup inner wall portion; the holding portion includes a cylindrical radially opposing portion arranged radially opposite the outer circumferential surface of the cylindrical seal portion; the horizontal gap is defined between the radially opposing portion and the cup inner wall portion; and an inner circumferential surface of the radially opposing portion and the outer circumferential surface of the cylindrical seal portion are arranged to together define a vertical gap continuous with the horizontal gap therebetween.
 7. The blower fan according to claim 2, wherein a lower end of the cylindrical seal portion is arranged at a level lower than that of a lower end of the cup inner wall portion; the holding portion includes a cylindrical radially opposing portion arranged radially opposite the outer circumferential surface of the cylindrical seal portion; the horizontal gap is defined between the radially opposing portion and the cup inner wall portion; and an inner circumferential surface of the radially opposing portion and the outer circumferential surface of the cylindrical seal portion are arranged to together define a vertical gap continuous with the horizontal gap therebetween.
 8. The blower fan according to claim 6, wherein the stator includes: an annular core back; a plurality of teeth arranged to project radially outward from the core back; and coils each of which is defined by a conducting wire wound around a separate one of the teeth; an inner circumferential surface of the core back is fixed to an outer circumferential surface of the radially opposing portion; and an upper end of the radially opposing portion is arranged at a level higher than that of an upper end of the core back.
 9. The blower fan according to claim 7, wherein the stator includes: an annular core back; a plurality of teeth arranged to project radially outward from the core back; and coils each of which is defined by a conducting wire wound around a separate one of the teeth; an inner circumferential surface of the core back is fixed to an outer circumferential surface of the radially opposing portion; and an upper end of the radially opposing portion arranged at a level higher than that of an upper end of the core back.
 10. The blower fan according to claim 1, wherein a lower end of the cylindrical seal portion is arranged at a level lower than that of a lower end of the cup inner wall portion; and the outer circumferential surface of the cylindrical seal portion includes an inclined surface which is angled radially inward with decreasing height between the lower end of the cup inner wall portion and the lower end of the cylindrical seal portion.
 11. The blower fan according to claim 1, wherein the outer circumferential surface of the cylindrical seal portion includes a recessed portion or a raised portion, while an inner circumferential surface of the cup inner wall portion includes a raised portion or a recessed portion to be fitted to the recessed portion or the raised portion of the outer circumferential surface of the cylindrical seal portion.
 12. The blower fan according to claim 1, wherein the bearing portion includes: a sleeve; and a bearing housing arranged to cover an outer circumferential surface and a lower surface of the sleeve.
 13. The blower fan according to claim 1, further comprising a housing arranged to accommodate the motor portion and the blades, wherein the housing includes: an upper plate portion arranged to cover an upper side of the blades; a lower plate portion arranged to cover a lower side of the blades, and arranged to have the motor portion fixed thereto; and a side wall portion arranged to cover a lateral side of the blades; at least one of the upper and lower plate portions includes an air inlet; and the upper plate portion, the side wall portion, and the lower plate portion are arranged to together define an air outlet on the lateral side of the blades. 